1. Field of the Invention
The present invention relates to a lamp unit. More specifically, the present invention relates to a lamp unit having a semiconductor light-emitting element as a light source.
2. Related Art
A conventional vehicular headlamp ordinarily has a constitution that enables the formation of a low-beam distribution pattern having a cut-off line on an upper end edge thereof. Consequently, the forward visibility of the host vehicle's driver can be ensured to the greatest extent possible while also ensuring that no glare is directed at pedestrians and the drivers of oncoming vehicles.
In recent years, a constitution employing an LED, unlike conventional incandescent lamps and discharge lamps, has been studied for use as a light source of the vehicular headlamp. The output per LED of a vehicular headlamp that uses an LED as a light source is smaller than that of an incandescent lamp and a discharge lamp. Therefore, the use of a plurality of LEDs to obtain a desired amount of light for the formation of a low-beam distribution pattern has also been studied.
Patent Document 1 describes a vehicular lighting fixture that combines a first optical unit, which has a semiconductor light-emitting element as a light source and is suited for forming a cut-off line, and a second optical unit, which has a semiconductor light-emitting element as a light source and is suited for widely diffusing a large amount of light.    [Patent Document 1] Japanese Patent Application Laid-Open (Kokai) No. 2008-243476